This application claims the priority of German Patent Document No. 197 56 700.2, filed Dec. 19, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a vehicle seat capable of being adjusted to adapt the seat position, in particular for motor vehicles.
In a known vehicle seat (DE 37 18 126 A1), the seat-length adjustment is positively coupled to a seat-height adjustment, so that, when the seat height is adjusted, a resulting overall movement of the vehicle seat takes place along an arc of a circle. This is intended to ensure that the driver, after adjusting the seat length for the purpose of setting the desired distance from the vehicle pedal assembly and after a subsequent adjustment of the seat height, does not have to correct the seat-length adjustment again in order to restore the distance from the vehicle pedal assembly, which otherwise changes during seat-height adjustment.
In present-day traffic situations, for adjustable seats, the correct setting of the head restraint after the correct seat position has been found is of great importance from the point of view of safety. The force introduced into the body of the seated person in the event of an accident must be in the right places in order to avoid detriment to health and physical injury. At the same time, the fact must be taken into account that the head and the rest of the body of the seated person are subjected to different acceleration. The force generated in the event of an accident typically acts in the region of the cervical vertebra of the spinal column and, even in minor accidents, easily leads to so-called SVS trauma if the head restraint is set incorrectly.
In a known vehicle seat (DE 44 09 046 C2), therefore, the height and inclination of the head restraint, too, can be adjusted in dependence on parameters of the seat setting, in such a way that the head cushion is always arranged in relation to the back of the seat user's head, which is favourable from a safety point of view. For this purpose, a control unit has a characteristic diagram, in which the values of dependently adjustable components of the vehicle seat, for example the back rest and the head restraint, are stored in relation to at least one vehicle-seat component, for example the seat part, which can be adjusted independently by the seated person. If, for example, the seat part is adjusted longitudinally by the seated person, adjusting devices for setting the back rest inclination and for adjusting the height of the head restraint are activated, depending on the values for this longitudinal seat adjustment which are retrieved from the characteristic diagram.
In a known head restraint (U.S. Pat. No. 4,729,146), an expandable airbag is arranged in the head cushion and is connected to a compressed-air system in order to be filled and emptied. For the correct setting of the head cushion, the seated person must increase or reduce the volume of the airbag by actuating corresponding valves, with the result that the front face of the head cushion is pivoted or pushed closer to the back of the seated person's head or further away from the back of the seated person's head. The possibility for adjusting the head restraint horizontally allows for the fact that, when the head restraint is raised for the purpose of adapting it to the body size of a larger driver, the horizontal distance between its head cushion and the back of the seated person's head is increased. This distance is also increased due to the fact that large drivers usually also set a greater inclination of the headrest. By virtue of the possibility for the horizontal displacement of the head cushion, this distance can be adjusted again and the head cushion brought up to the back of the seated person's head, so that it is set as well as possible in terms relevant to safety.
Investigations have shown, however, that, although many seat users adapt the seat position to their wishes by an appropriate seat adjustment, they do not set the head restraint correctly in the best possible way for their safety. In the event of an accident, therefore, physical injury, in particular injuries to the head and cervical vertebrae occur, which could have been avoided if the head restraint had been set correctly. Moreover, the known head restraint thus described has the disadvantage that, even when the head restraint is set correctly, damage, albeit considerably reduced, may occur in the region of the cervical vertebra as a result of the so-called rubber-ball effect. If the head cushion is adjusted to an extreme degree (that is, the airbag is very highly inflated), in the event of an accident, the air of the air cushion in the airbag is already compressed or is compressed excessively due to the impact of the head and, as a result, after impact accelerates the head forward again.
The object of the present invention is to improve a vehicle seat of the type mentioned in the introduction, so that when the seat is occupied by a person of any size, the head restraint is always correctly set automatically in terms relevant to safety by simple means in dependence on the seat adjustment previously carried out and, in the event of impact, constitutes reliable injury-preventing absorption protection for the seated person's head.
The adjustable vehicle seat according to the present invention has the advantage that, after the seat position has been set individually by a person using the seat, the head restraint is correctly set automatically, without the assistance of the seat user, simply by a variation in the filling quantity in a medium reservoir. The seated user is thus protected as well as possible in accident situations. At the same time, a pressure limiter connected to the medium reservoir prevents the medium reservoir from being compressed excessively during the horizontal adjustment of the head cushion, so that the medium reservoir remains sufficiently soft to cushion the impact of the head by the absorption of energy and thus to prevent the head from being thrown back. Taking into account the parameters of the seat part and back rest adjustments carried out, such as the longitudinal displacement of the seat part, the seat part inclination, the height of the seat part above the vehicle floor, the inclination of the back rest and the like, ensures that the head cushion is set correctly in terms of safety, even when the sitting posture of the seat user differs widely from the standard sitting posture envisaged in the seat design.
According to a preferred embodiment of the present invention, a motor-operated head-restraint adjuster is additionally provided, which, when activated, adjusts the height of the head cushion in relation to the top edge of the back rest according to a control signal supplied by the control unit. The control signal is determined by the control unit from the parameters of the seat part and back rest adjustments carried out. By means of this additional automatic adjustment component of the head restraint in the vertical direction, the range of adjustment of the head-restraint setting can be increased considerably and can equally embrace extremely small and extremely large seat users who may have sitting postures which differ to a great extent. Moreover, in the middle range of adjustment, the change in the filling quantity of the reservoir for adaptation to seat users having a different body size and/or sitting posture can be kept relatively small, and the adaptation time can be reduced appreciably as a result of the simultaneous execution of both the vertical and the horizontal adjusting movements of the head cushion.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.